Field of the Invention
The present invention relates to an improved process for hydrogenation of heavy oil. More particularly it is concerned with an industrially advantageous process for hydrogenation of heavy oil whereby a middle distillate fraction of high added value, such as kerosene or light oil can be produced in high yield.
In recent years, with introduction of substitute energy in the general industry or electric power field, the amount of consumption of heavy fractions such as heavy fuel oil, etc. tends to decrease. On the other hand, the amount of consumption of gasoline as a fuel for public or transportation purpose, or a middle distillate fraction such as jet fuel, korosene, light oil is increasing. The proportion of heavy oil in crude oil imported into Japan tends to increase.
Under such circumstances, it is important that an intermediate fraction such as gasoline, kerosene or light oil is efficiently produced by hydrogenating heavy oil such as atmospheric residual oil, vacuum residual oil, tar sand oil or oil shale oil.
In hydrogenation of heavy oil, catalytic activity drops as a result of deposition of carbon and undesirable metals. It is known, however, that in hydrogenation of suspension bed system using a powdery solid catalyst, deposition of carbon or metal are not so severe and thus a reduction in catalytic activity is advantageously small.
In hydrogenation of such heavy oil, it is advantageous from an economic standpoint to use a catalyst which is of high activity and inexpensive. For this reason, an attempt to use various waste catalysts used in oil refinery has been made. For example, a method using a spent FCC catalyst (U.S. Pat. No. 4,082,648) and a method using a waste direct desulfurization catalyst (Japanese Patent Kokai Koho No. 40806/1979) are disclosed.
In these spent catalysts, vanadium, nickel, etc. effective as catalyst components for hydrogenation of heavy oil are accumulated on the surface thereof. Thus they can be used as catalysts for hydrogenation of heavy oil. The method using a spent FCC catalyst, however, has disadvantages in that the activity of the waste catalyst is not sufficiently high, the amount of coke formed is large, and the yield of the desired intermediate fraction is low. In the case of the method using a spent direct desulfurization catalyst, the spent catalyst is poor in mechanical strength although it is satisfactory in respect of catalytic activity. More specifically, the attrition index of the spent direct desulfurization catalyst is about 40 wt %/30 hours (about 3 wt %/30 hours in the case of the spent FCC catalyst). Thus the loss of the catalyst due to attrition is inevitably accompanied.